Madness Interactive

Monster Madness: Grave Danger
$39.99
I tried the demo of this game, and fell in love with it. I bought it for a great price (10 dollars plus shipping). It has a fun, classic feel to the game play, and even though it may be more "kiddie-centric", it really has some gameplay value for older players (I'm 35!). On top of that, it has 4 player simultaneous mode! Too many games nowadays are lacking this type of feature. For parents, it's a great game to play with the kids. And it has plenty of upgradeable stuff and little tidbits to keep adults interested too (see if you can pick out all of the old monster movie cliches ;) ).

Quizmo Math Madness (Interactive Quiz Game)
$3.99
Spiralbound, Interactive Quiz Game, 464 Painless Questions and Instant Answers

Virtual Reality Madness 1996
$49.99
There is no better way to start learning about VR than starting with this book. Ron Wodaski provides great tutorials for using great VR software such as Virtus Walkthrough and Vistapro, both of which are included on the CDs. Also included are chapters dedicated to the big, expensive 3d rendering program, 3D Studio(not included). Possibly the best part about VR Madness '96 is that it comes with 3 CD's loaded with VR apps, utilities, and games.

Monster Madness: Battle for Suburbia
$39.99
This single game that you can also play with a friend is pretty fun, and is similar to Marvel Ultimate Alliance except it's a city filled with zombie/undead. The controls and character movements/shooting is a bit clunky and would have been a much better game if those issues were not present. I got the game brand new for only about $5 so that was awesome; but I would not pay close to $10 (including shipping) for this game, new or used.